Monolithic Cross-Sections. Various types of glass and
plastics are available for use as monolithic glazing. This
paragraph describes the following types of monolithic glazing:
Heat Strengthened Glass
Thermally Tempered Glass
Chemically Treated Glass
In general, monolithic glass cross-sections are
vulnerable to forced entry and ballistic attacks. Once the glass
fails, there is nothing to hold the broken fragments in place.
This allows the fragments to fly or fall out, injuring personnel
and yielding access to assets which need protection. Monolithic
glass glazing, which fails as a result of a bomb attack, will
permit jetting of unacceptable blast overpressure into the
interior of a building and present an increased fragment hazard.
For these reasons, monolithic glass is not recommended for use in
Annealed Glass. Annealed glass is the most common form
of glass available. Depending on manufacturing techniques, it is
also know as plate, float, or sheet glass.
During the manufacturing process, annealed glass is
cooled slowly without tight controls. This process yields a
product which has very little residual compressive surface stress
and large variations in strength. When compared with tempered
glass, annealed glass is of relatively low strength.
Upon failure, annealed glass fractures into razor-
sharp, dagger-shaped fragments. For this reason, monolithic
annealed glass is not recommended for use in blast resistant
Heat Strengthened Glass. Heat strengthened, heat
treated, or semi-tempered glass exhibits neither the higher
tensile strength nor the small cube-shaped fracture pattern
associated with thermally tempered glass.
The cooling process of heat strengthened glass is
controlled more tightly than annealed glass but less than
thermally tempered glass. This results in large variations in the